Prior intervertebral implants are disclosed by U.S. Pat. No. 5,314,477 and U.S. Patent Publication Application No. 2004/0215198. These references disclose implants which replace a disc removed from the intervertebral space using a total disc replacement procedure. These and other devices have been used in the field of disc replacement which involves the insertion of an artificial intervertebral disc implant into the intervertebral space between adjacent vertebrae, and which allows limited universal movement of the adjacent vertebrae with respect to each other.
Recently, several non-fusion techniques have emerged which treat different stages of degenerative disc disease other than total disc replacement. One of these technologies includes nucleus replacement devices which have been developed to treat early stages of degenerative disc disease. The goal of these technologies is to replace only the nucleus pulposus of the intervertebral disc and to leave the annulus and the ligaments as intact as possible.
Although these prior nucleus replacement intervertebral devices provide limited universal movement, there is a need in the art for new and improved intervertebral devices which provide enhanced universal movement of the adjacent vertebrae with respect to each other.